Chemical kinetics is the study of rates at which a chemical reaction occurs. Such an investigation provides understanding of the reaction mechanisms along with the identification of possible reaction intermediates.
Of particular interest are biochemical reactions, such as protein conformational change and enzymatic catalysis, which are responsible for many important biochemical and physiological processes. The protein conformational changes or the formation of enzyme-substrate complex intermediates may occur within microseconds, making the detection of intermediates technically challenging.
Conventional techniques for kinetic study generally involve spectroscopic methods, such as UV and fluorescence spectroscopy. These methods have the benefit of high time resolution, for example, femtosecond or attosecond time scales. However, these techniques also require chromophoric substrates or radioactive labeling.
Mass spectrometry (MS)-based approaches to study kinetics are being developed, particularly with the advent of electrospray ionization (ESI). Notably, the time-resolved ESI-MS work based on elegant designs for reactant solution mixing have been established to allow the monitoring of reaction kinetics with time resolution ranging from milliseconds to seconds.
The striking advantages of using conventional MS detection over spectroscopic detection are that conventional MS has high chemical specificity and does not require chromophoric substrates. Nevertheless, it is necessary to further improve the time resolution of MS methods, which is required for MS kinetic study, to help to capture the possible intermediate and to investigate the mechanism of fast reaction processes.